Picture-wings

Sunday, 7th July 2002, West Yorkshire

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picture wings There's a stir as I walk past the pond. A wisp of small flies swishes up for a moment then settles again on the carpet of duckweed. I crouch down to take a closer look; there are 30 or 40 of them, bronzy in colour, up to 8mm long.

The flies are using the pond as a lek; a display ground where the males vie with each other to attract the females. The males, which are larger than the females, have brown patches, edged with a crescent of a lighter shade, at the end of each wing.

picture wing female Their aim is to entice a female to land close by or, failing that, to land in front of a female and attract her attention by performing a wing-waving display; wings out, wings forward, wings back - a motion like rowing a boat or waving semaphore signals. Sometimes they'll repeat this a few times at about the interval that it would take you to say, in a leisurely way, 'one, two - one, two.'

The female often plays hard to get. She'll turn away on the spot. The male (left) flies up and settles to face her again, an inch or so from her, and performs his routine again. The female might turn again - in which case he'll fly around again to face her - or she might get bored of the whole thing and fly off. Occasionally the dance will result in a mating. Sometimes a male will display to another male who will wave his wings as if to show he's not a female and the dance will end there.

There's a lot of activity and the whole thing looks like a disco in full swing, except the females aren't dancing in a circle around a pile of handbags.

I'm calling them picture-wing flies, but I'm just going by the wing-waving behaviour. True picture-wings seem to be smaller than these, and with motlier wing patterns.

I've also seen the same flies, in smaller numbers, gathered around an almost dried-up puddle.

Dolichopodid flies

A local naturalist, John Coldwell, e-mailed me with this information:

You may (or may not!) like to know that your 'picture winged' flies were almost certainly the dolichopodid Poecilobothrus nobilitatus.

Red-eyed Fly

Here's another small fly but this one is tiny, only 3.5 mm long, 5 mm if you include the wings. It's the time of year when one or two dead insects start appearing on the desk below the studio window. With the aid of my 30x pocket microscope

I sketch the details of the red multi-lensed eyes, the whiskers on its head and thorax (which I guess help it judge its movement through the air), the hairy legs, the veined wings and the stumpy thorax. The little microscope is handy to carry about but it's got such a small depth of field that I have to change the focus five or six times to sketch the whole fly. I know I don't have a chance of identifying it.

The little mushroom shaped organ that I've drawn in more detail is one of a pair of halteres. You can see in the sketch that it sits just behind the wing. In two-winged flies, also known as true flies or Diptera, what would be the rear pair of wings in a dragonfly, bee or butterfly are modified into these organs which are probably an aid to balance in flight.

Richard Bell,
wildlife illustrator
E-mail; 'richard@willowisland.co.uk'

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